Multilayer ohmic contact for p-type semiconductor and method of making same

Abstract

Novel ohmic contacts are provided for p-type semiconductor compounds comprising at least one of the metals of Class IIB of the Periodic Table of Elements and one of the non-metal elements of Class VIA of the Periodic Table of Elements, as well as a method for forming such novel ohmic contacts. These ohmic contacts comprise a multilayer metal contact wherein the first layer provides a lasting stable contact with the p-type semiconductor; the additional layers provide the necessary electrical conductivity for the contact to be efficient.

What is claimed is: 
     
       1. An ohmically conductive contact for a thin film p-type semiconductor compound formed of at least one of the metal elements of Class IIB of the Periodic Table of Elements and at least one of the non-metal elements of Class VIA of the Periodic Table of Elements comprising a first layer of copper contiguous with said p-type semiconductor compound and having a layer thickness of from about 5 Angstroms to about 50 Angstroms and a second layer thereon comprising at least a second conductive metal. 
     
     
       2. The ohmic contact in accordance with claim 1 wherein said p-type semiconductor compound is cadmium telluride. 
     
     
       3. The ohmic contact in accordance with claim 1 wherein said p-type semiconductor compound is mercury cadmium telluride. 
     
     
       4. The ohmic contact in accordance with claim 1 wherein said first layer of copper has a layer thickness of from about 10 Angstroms to about 30 Angstroms. 
     
     
       5. The ohmic contact in accordance with claim 1 wherein said second layer comprises nickel, gold, silver, antimony, molybdenum, chromium, tellurium, platinum, palladium and mixtures and alloys thereof. 
     
     
       6. The ohmic contact in accordance with claim 1 wherein said second layer comprises nickel, gold, chromium, and mixtures and alloys thereof. 
     
     
       7. The ohmic contact in accordance with claim 1 wherein said second layer is nickel. 
     
     
       8. The ohmic contact in accordance with claim 1 wherein the thickness of said second layer is at least about 1,000 Angstroms. 
     
     
       9. A thin film photovoltaic device having an optically transparent substrate, a conductive transparent film disposed on said substrate, an n-type semiconductor layer formed on the conductive transparent film, a p-type semiconductor layer deposited contiguously onto the n-type semiconductor layer and forming a junction therewith, and an ohmically conductive contact disposed over the p-type semiconductor layer; the ohmically conductive contact comprising a first layer of copper contiguous with said p-type semiconductor layer and having a layer thickness of from about 5 Angstroms to about 50 Angstroms and a second layer deposited thereon comprising at least a second conductive metal. 
     
     
       10. The photovoltaic device in accordance with claim 9 wherein said n-type semiconductor layer is CdS and said p-type semiconductor layer is CdTe. 
     
     
       11. The photovoltaic device in accordance with claim 9 wherein said layer of copper has a layer thickness of from about 10 Angstroms to about 30 Angstroms. 
     
     
       12. The photovoltaic device in accordance with claim 9 wherein said second layer comprises nickel, gold, chromium, and mixtures and alloys thereof. 
     
     
       13. The photovoltaic device in accordance with claim 9 wherein said second layer is nickel. 
     
     
       14. The photovoltaic device in accordance with claim 9 wherein the thickness of said second layer is at least about 1,000 Angstroms.